/Engine/Source/Runtime/Experimental/Iris/Core/Public/Iris/Serialization/NetBitStreamUtil.h
AFNetSerializeris needed for replication support of a certain type. Most types that can be marked as UPROPERTY are already supported. Types that aren't supported or need special support will emit warnings when descriptors are built for a UCLASS, USTRUCT or UFUNCTION. Find below how to implement one.
namespace UE { namespace Net { enum ESparseBitArraySerializationHint { None, ContainsMostlyOnes, } } }